The present invention is directed to filter media having microbiological interception capability, filtration systems containing such filter media, and methods of making and using same.
Modern consumer water filters often provide xe2x80x9chealth claimsxe2x80x9d including reduction of particulates, heavy metals, toxic organic chemicals, and select microbiological threats. These filtration systems have been able to intercept microorganisms such as Cryptosporidium and Giardia using roughly 1.0 micron structures. However, in order to provide microbiological interception of even smaller microbiological threats such as viruses, a filter medium having a sub-micron microporous structure is required. Prior art filtration systems often attempt to achieve broad microbiological interception using filter media with insufficiently small pore size and with poor physical integrity. The balance between the necessary pore structure required for successful microbiological interception and satisfactory filter performance has not been achieved.
The present invention is directed to, in a first aspect, a filter medium comprising: a microporous structure comprising an array of active particles, the microporous structure having a mean flow path of less than about 2 microns; and a microbiological interception enhancing agent comprising a cationic material having a medium to high charge density and a molecular weight greater than about 5000 Daltons, adsorbed on at least a portion of the microporous structure, and a biologically active metal in direct proximity to the cationic material and also on at least a portion of the microporous structure.
In another aspect, the present invention is directed to a filter system comprising: a housing having an inlet and an outlet; a filter medium situated within the housing in fluid communication with the inlet and outlet, the filter medium comprising: a microporous structure having a mean flow path of less than about 2 microns comprising active particles of activated carbon, activated alumina, zeolites, diatomaceous earth, silicates, aluminosilicates, titanates, bone char, calcium hydroxyapatite, manganese oxides, iron oxides, magnesia, perlite, talc, polymeric particulates, clay, iodated resins, ion exchange resins, ceramics, or combinations thereof; and a microbiological interception enhancing agent comprising a cationic material having a high charge density, a molecular weight greater than about 5000 Daltons and having an associated counter ion therewith, the cationic material adsorbed on at least a portion of the microporous structure, and wherein a biologically active metal is caused to precipitate with at least a portion of the counter ion associated with the cationic material, wherein a microbiologically contaminated influent flowing through the housing and contacting the filter medium has at least about 4 log reduction in microbiological contaminants in an effluent flowing from the housing.
In yet another aspect, the present invention is directed to a process of making a filter medium having enhanced microbiological interception capability comprising the steps of: providing active particles having an average particle size of about 0.1 microns to about 5,000 microns; treating the active particles with a microbiological interception enhancing agent comprising a cationic material having a high charge density and a molecular weight greater than about 5000 Daltons in combination with a biologically active metal; and forming the treated active particles into a microporous structure having a mean flow path of less than about 2 microns.
In still yet another aspect, the present invention is directed to a process of making a filter medium having enhanced microbiological interception capability comprising the steps of: providing active particles having an average particle size of about 0.1 microns to about 5,000 microns;
coalescing the active particles into a microporous structure having a mean flow path of less than about 2 microns; and treating the microporous structure with a microbiological interception enhancing agent comprising a cationic material having a high charge density and a molecular weight greater than about 5000 Daltons in combination with a biologically active metal.
In a further aspect, the present invention is directed to a method of removing microbiological contaminants from a fluid comprising the steps of providing a filter medium comprising a microporous structure comprising active particles and having a mean flow path of less than about 2 microns; and a microbiological interception enhancing agent comprising a cationic material having a medium to high charge density and a molecular weight greater than about 5000 Daltons in combination with a biologically active metal, adsorbed on at least a portion of the microporous structure; contacting a microbiologically contaminated fluid to the filter medium for a period of time of less than or equal to about 12 seconds; and obtaining an effluent having greater than about 4 log reduction of microbiological contaminants.